Yeah, that's what I meant by "mature". Agda also has a js backend, but neither one can really stand alone. Haskell is closer, but GHCJS is still very much a second class citizen of the ecosystem.
Clean also has WASM as the compile target via its IR, and its tooling is great. Unfortunately though I couldn't find any sort of a community when I was looking into it, but other than this the language looks quite mature and very industry-oriented.
Then there's Lean which also can compile to WASM via some sort of a bridge, it has decent tooling but the ecosystem is still nonexistent.